A spray nozzle assembly of the foregoing type is shown and described in U.S. Pat. No. 5,921,472, the disclosure of which is incorporated by reference. Such spray nozzle assemblies typically include a nozzle body which defines a mixing chamber into which a liquid hydrocarbon and pressurized gas, such as steam, are introduced and within which the liquid hydrocarbon is atomized. To enhance liquid atomization within the mixing chamber, an impingement pin extends into the chamber and defines a liquid impingement surface on the center line of the mixing chamber in diametrically opposed relation to the liquid inlet against which a pressurized liquid stream impinges and is transversely dispersed and across which pressurized steam from a gas inlet is directed for further interaction and shearing of the liquid into fine droplets. The atomized liquid within the mixing chamber is directed under the force of the pressurized steam through an elongated tubular barrel, commonly disposed within a wall of the catalytic reactor riser, for discharge from a spray tip at a downstream end thereof within the riser.
The nozzle body, which defines the mixing chamber and receives the impingement pin, a liquid hydrocarbon inlet, and a pressurized steam inlet, is a relatively expensive component of the spray nozzle assembly. The nozzle body commonly is machined from solid metal stock, which due to its complexity, is laborious and time consuming, substantially increasing the cost of the nozzle assembly. Moreover, since the end of the impingement pin is disposed within the path of travel of the pressurized stream, it further is susceptible to erosion from the steam injection, causing the necessity for periodic costly replacement. For effective operation, it further is required that the atomized liquid hydrocarbon and steam continue to intermix during travel through the elongated barrel of the nozzle assembly without undesirable stratification.